Each element is defined by the number of protons in its nucleus. This number is known as the atomic number, and it determines the element's identity. For example, all atoms with one proton are hydrogen atoms, all atoms with two protons are helium atoms, and so on.
The electrons in an atom determine its chemical properties. Electrons can be transferred or shared between atoms, forming chemical bonds. The number of electrons in an atom's outermost shell, known as the valence electrons, determines how it interacts with other atoms.
Atoms can combine with other atoms to form molecules and compounds. A molecule is a group of atoms that are held together by chemical bonds. A compound is a substance that contains two or more elements chemically bonded together.
The properties of an element depend on the properties of its atoms. For example, the chemical reactivity of an element is determined by the number of valence electrons it has. Elements with a high number of valence electrons are more reactive than elements with a low number of valence electrons.
The smallest components of elements having all chemical properties are atoms. Atoms are the building blocks of matter, and they determine the chemical properties of elements.
